Jet propulsion apparatus and operating method

ABSTRACT

Vanes are mounted on jet engine nozzle or a plug associated therewith for movement between a position wherein they permit normal flow of the exhaust gas of the engine in a direction parallel with the longitudinal axis of the nozzle, and a position wherein they cause the exhaust gas to whirl about said nozzle axis as it travels longitudinally thereof. When the vanes whirl the exhaust gas its rate of mixing with atmospheric air is increased, thus suppressing jet noise.

United States Patent MacDonald 5] Mar. 7, 1972 [54] JET PROPULSIONAPPARATUS AND OPERATING METHOD [72] Inventor: Howard R. MacDonald, SanDiego, Calif.

[7 3] Assignee: Rohr Corporation, Chula Vista, Calif.

[22] Filed: Feb. 2, 1970 [21] Appl. No.: 7,520

[52] US. Cl. ..18l/33 HC, 181/33 HD, 239/127.3,

239/265.17 [51] Int. Cl. ..F0ln l/l4, FOln l/18, B64d 33/06 [58]FieldofSearch ..l8l/33,' 33.2, 33.221,33.222,

[56] References Cited UNITED STATES PATENTS 2,664,700 1/1954 Benoit..l8l/33.222 2,944,623 7/1960 Bodine l 81/ 33.222 2,696,709 12/1954Oulianoff ..181/33.222

3,036,429 5/1962 Schairer 1 81/3322] 3,550,721 12/1970 Bruner 181/51FOREIGN PATENTS OR APPLICATIONS 874,496 8/1961 Great Britain..239/265.39

885,093 12/1961 Great Britain... ..18l/33.222 1,525,355 4/1968 France..181/33.222 1,524,105 4/1968 France ..l8l/33.221

Primary Examiner-Robert S. Ward, Jr. Anomey-George E. Pearson 571ABSTRACT Vanes are mounted on jet engine nozzle or a plug associatedtherewith for movement between a position wherein they permit normalflow of the exhaust gas of the engine in a direction parallel with thelongitudinal axis of the nozzle, and a position wherein they cause theexhaust gas to whirl about said noule axis as it travels longitudinallythereof. When the vanes whirl the exhaust gas its rate of mixing withatmospheric air is increased, thus suppressing jet noise.

3 Claims, 12 Drawing Figures PATENTEUHAR 11912 SHEET 1 UF 2 INVENTOR.

HOWARD R. MACDONALD BY EMQM AT TORN E Y PATENTEDMAR (I972 3,647,020

sum 2 [1F 2 INVENTO HOWARD R. MACDON BY EMDM ATTORNEY JET PROPULSIONAPPARATUS AND OPERATING METHOD SUMMARY OF THE INVENTION This inventionrelates to aircraft jet propulsion apparatus and a method of operatingthe same. More particularly, the invention provides means forsuppressing noise generated by the flow of high-velocity jet engineexhaust gas through the atmosphere, as well as means for more rapidlydecelerating an aircraft after it has landed.

The advantages of the invention may be attained through variousembodiments thereof, all of which are arranged to induce, at a selectedtime, vortical motion in the exhaust gas discharged from an aircraft jetengine. In a preferred embodiment of the invention vanes are mountedwithin a jet engine thrust nozzle and project radially therefrom at theforward portion of the nozzle section, said vanes being rotatablebetween (I an inoperative position wherein they are feathered in theexhaust gas stream discharged through said nozzle and thus have littleeffect on the flow thereof and (2) an operative position wherein eachvane is disposed. at an angle to the longitudinal axis of said nozzle sothat exhaust gas impinges against one side thereof and is therebydeflected circumferentially of said nozzle (i.e., the deflected exhaustgas is given a velocity component in a direction transverse to thelongitudinal axis of the nozzle). The portion of exhaust gas which isdeflected by the vanesexerts deflecting force against the remainder ofthe exhaust gas, and thus the jetstream discharged to the atmosphere iswhirled about the longitudinal axis of the thrust nozzle. The transversevelocity component of the exhaust gas causes the jetstream to flow awayfrom the longitudinal axis of the nozzle when it reaches the atmosphere.Hence the angle at which the boundary of the jetstream diverges from theaft end of the nozzle is greater than that associated with normal linearflow of said jetstream (i.e., flow of the jetstream when the vanes arefeathered and no vortical motion is imparted thereto). This increasedangle of divergence of the jetstream and its whirling motion result infaster mixing of the hot, high-velocity exhaust gas with cool,relatively low-velocity atmospheric air and thereby suppresses the noisegenerated by the flow of the jetstream through the atmosphere. In asecond embodiment oftheinvention vanes are pivotally mounted on a conethe base of which is fixedly attached to the aft bearing housing of ajet engine, and are movable between an inoperative position wherein theylie against the cone and an operative position wherein they extendradially from the latter and deflect exhaust gas circumferentially of athrust nozzle as in the first described embodiment. In a thirdembodiment vanes are mounted on the aft edges of a lobed thrust nozzleand move between an inoperative position extending longitudinally fromsaid edges and an operative position extending laterally therefrom boththe exhaust gas streams which are discharged from the lobes of thenozzle and the airstreams which flow between said lobes being deflectedby the respective vanes when the latter are in the operative position sothat said streams whirl about a line coincident with the longitudinalaxis of said nozzle and extending downstream therefrom. Thus the secondand third embodiments are also adapted to vary the divergence of jetengine exhaust gas streams and impart vortical motion thereto andthereby suppress the noise of such streams at any selected time.

When apparatus in accordance with the invention is operated to impartvortical motion to ajetstream as described, the thrust of the stream isreduced. This result permits a jetengine to be operated at a high-powerlevel during the landing approach of an aircraft, but without producinggreater thrust than is usable at this time. After the aircraft haslanded on a runway, thrust reversers can be deployed to reverse thethrust of the engine at the same time the apparatusof the invention isoperated to provide normal flow of the jetstream. High reverse thrust isthus obtained as soon as the thrust reversers are deployed, whereasordinarily maximum reverse thrust is .the term thrust nozzle,

reached only after some time has elapsed in increasing the thrust outputof an engine while an aircraft is rolling down a runway. 1

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a jet enginehousing and thrust nozzle assembly in which a first embodiment of theinvention is incorporated, the drawing illustrating only the aft portionof said housing and components of the embodiment which are disposedwithin said nozzle being represented by broken lines;

FIGS. 2 and 3 are end elevations of the same apparatus, respectivelyillustrating inoperative and operative positions of vanes utilizedtherein; I

FIGS. 4-7 are corresponding views of another jet engine housing andthrust nozzle assembly in which a second embodiment of the invention isincorporated, FIGS. 4 and 5 respectively being side and end elevationswhich illustrate an in operative position of vanes utilized therein andFIGS. 6 and 7 respectively being side and end elevations whichillustrate an" operative position of the same vanes:

FIGS. 8-10 are corresponding views'of still another jet engine housingand thrust nozzle assembly. in which a third embodiment of the inventionis incorporated, FIGS. 8 and 9 respectively being side and endelevations which illustrate an inoperative position of vanes utilizedtherein and FIG. 10

being an end elevation which illustrates an operative position of thesame vanes; v FIG. 11 is a fragmentary longitudinal section of a plugmounted at the aft endof the nozzle illustrated in FIGS. 8l0, togetherwith typical parts of an actuating mechanism which moves components ofthe third embodiment; and

FIG. l2 is a fragmentary cross section of the same plug, illustratingthe same parts of said mechanism.

DETAILED DESCRIPTION First Embodiment In FIG. 1 reference number 20designates generally a tubular housing enclosing a jet engine 22andhaving a frustoconica] thrust nozzle 24 coaxially mounted on the aftend 26 thereof. Housing 20.may be the fuselage or an engine nacelle ofan aircraft, and engine .22 may be either a turbojet or a turbofanengine (although to simplify the drawings the engine is illustratedschematically as a turbojet engine). Hence it should be pointed out thatthe term exhaustgas, as. used in the followingdescription and inclaimsappended hereto, is to be considered to apply to either the combustiongas of a turbojet engine or a mixture of. both the combustion gas andfanair of a turbofan engine. Furthermore, it shouldbe understood that asused in the description and claims, is intended to apply to the entirelength of av conduit through which exhaust gas of ajetengine isdischarged to the atmosphere. This definition of thrust nozzle" is madebecause vanes 28 which are mounted in the forward portion of nozzle 24may, in some embodiments of the invention, be located in a duct which ina strict technicalsense does not constitute part. of a thrust nozzlebutonly serves to conduct gas from a jet engine tothe nozzle. As can beseen in FIGS. 2 and 3, there are a plurality of vanes 28 each fixedlyattached at one end to a rod 30 .which passes through a hole in the wallof nozzle 24 and which is rotatable about the longitudinal axis of saidhole. More specifically, each rod 30 is coaxial with the vane mountedthereon, and the longitudinal axes of the rodvane assemblies lie in aplane perpendicular-to the longitudinal axis of the nozzle and areevenly spaced aroundand extend radially from said axis as illustrated.An arm 32 extends laterally from the outer end of-each rod 30 and isconnected at its frceend to the drive shaft 34 of an actuator 36 mountedon housing 20 adjacent the aft end thereof. Actuators 36 may be of anysuitable type and are adapted to be operated from a point remote fromthe engine housing so as to move drive shafts 34 longitudinally of saidhousing and thereby simultaneously rotate vanes 28 between theinoperative position illustrated in FIG. 2 and the operative positionillustrated in FIG. 3. Operation of the First Embodiment When the vanesare in the inoperative position their sides extend longitudinally ofnozzle 24, and therefore there is virtually no interference with thelinear flow through the nozzle of exhaust gas discharged from engine 22.However, when the vanes are rotated to the operative position they areall disposed at a predetermined angle relative to the longitudinal axisof the nozzle (all vanes being turned in the same direction) and exhaustgas impinges upon the sides of the vanes and is thereby deflected in acircumferential direction relative to the. nozzle. The portion ofexhaust gas which is deflected by the vanes exerts deflecting forceagainst the remainder of said gas, and thus the jet stream comprised ofsaid gas is whirled about the longitudinal axis of nozzle 24 as it flowsrearwardly. When the exhaust gas reaches the aft end of the nozzle itsvelocity component transverse to the longitudinal axis of the nozzlecauses the gas to flow away from said axis (i.e., away from a line whichis coincident with the iongitudinal axis of the nozzle and which extendsrearwardly from said nozzle). Hence, as pointed out hereinbefore, whenthe vanes are rotated to their operative position the angle ofdivergence of the jetstream from the nozzle is increased. The whirlingmotion of the jetstream and the resultant increase in its frontal areaincrease the volume of atmospheric air that is contacted with theexhaust gas at any given distance downstream from the thrust nozzle, andconsequently the rate of mixing of the hot, high-velocity exhaust gaswith the cool, relatively low-velocity air is greater than it is whenthe exhaust gas is discharged in a narrow laminar jetstream. It will beunderstood by persons skilled in the art of jet propulsion that thisincrease in the rate of mixing of the exhaust gas with atmospheric airsuppresses the noise associated with the operation of a jet engine.Sound suppression of the engine, or engines, of an aircraft is generallymost needed at the time the aircraft is taking off and climbing fromconjested airports when high thrust is being produced by said engines.Thus actuators 36 are operated to move vanes 28 to their operativeposition as the aircraft equipped therewith is taking off. Since thevelocity component of the exhaust gas which is transverse to thelongitudinal axis of nozzle 24 does not provide thrust, the vorticalmotion induced in the jetstream to achieve sound suppression isaccompanied by a decrease in thrust. The decrease in thrust at the timeof takeoff is a disadvantage but is outweighed by the reduction in thenoise produced by an aircraft which must by necessity fly at a lowaltitude over urban areas surrounding airports at major cities.

When an aircraft equipped with the described sound suppressing apparatusis in cruise flight or when full power is needed for emergencyconditions during take off or landing, vanes 28 are placed in theirinoperative position so that the exhaust gas flows linearly throughnozzle 24 and develops full thrust. During normal landing approach thevanes are preferably again rotated to their operative position, whichreduces the exhaust noise and thrust produced by engine 22 whilepermitting it to be operated at a higher power level than would bepossible for the same engine during landing approach in an aircrafthaving conventional propulsion apparatus. As soon as the aircraft landson a runway thrust reversers associated with housing and nozzle 24(which may be of any conventional type and therefore are notillustrated) are deployed to reverse the direction of travel of theexhaust gas issuing from said nozzle and actuators 36 are simultaneouslyoperated to rotate vanes 28 to their inoperative position. Thus thethrust of engine 22 at high power level is immediately available todecelerate the aircraft when it lands on a runway. This is not possiblein the operation of conventional propulsion apparatus, wherein an enginemust be operated at a reduced power level during landing approach so asto produce less thrust and then stepped up in rotational speed after theaircraft has landed in order to developed maximum reverse thrust inconjunction with thrust reversers. It should be noted in connection withthis use of vanes 28 that the amount of thrust loss which results fromthe vortical motion imparted to the exhaust gas by said vanes dependsupon the amount of deflection of said gas circumferentially of nozzle28. Therefore actuators 36 can be arranged to rotate the vanes todifferent angles during takeoff and landing approach, so as to therebymake the thrust loss resulting from the aforesaid vortical motion lessduring takeoff than during landing approach, while still inducingsufficient vortical motion at takeoff to provide adequate soundsuppression. Furthermore, there is laminar flow in ajet engine only atcertain optimum operating conditions and at other times there is swirlin the exhaust gas which reduces thrust. However, vanes 28 can berotated as required to eliminate this undesirable swirling of exhaustgas during cruise flight, thus increasing thrust and reducing fuelconsumption. Second Embodiment of the Invention In FIG. 4 referencenumber designates generally a second tubular aircraft housing enclosinga jet engine 122 which may be of either the turbojet or turbofan type(the drawings being simplified by illustrating a turbojet engine). As inthe case of the first described apparatus, housing 120 has afrustoconical thrust nozzle 124 coaxially mounted on the aft end 126thereof. In addition, a conical nozzle plug 128 is fixedly mounted onthe aft bearing housing 130 of engine 122, this plug being hollow andcoaxial with nozzle 124. Vanes 132 are pivotally mounted on the plug formovement between I) an inoperative position (illustrated in FIGS. 4 and5) wherein the vanes are disposed adjacent said plug and extend axiallythereof and (2) an operative position (illustrated in FIGS. 6 and 7)wherein the vanes extend laterally from said plug and deflect exhaustgas of engine 122 circumferentially of nozzle 124 to thereby impartvortical motion thereto. More specifically, each vane 132 is fixedly andcoaxially mounted on one end of a bar 134, and the other end of this baris in turn pivotally connected to plug 128 for rotation about an axistan-' gential to the forward portion of the wall thereof, the axes ofrotation of all of the bars 134 and vanes 132 thereon lying in a commonplane perpendicular to the longitudinal axis of nozzle 124. Bars 134 areevenly spaced apart circumferentially of plug 128, and the vanes arerespectively attached thereto so that when the bars are moved to theposition illustrated in FIGS. 6 and 7 said vanes are disposed at apredetermined angle relative to the longitudinal axis of the nozzle (allvanes of course being turned in the same direction). The movement of thebars and vanes between the aforesaid inoperative and operative positionsis effected by means of amechanism such as that described andillustrated in US Pat. No. 3,572,464, issued on Mar. 30, 1971, by theinventor of the herein disclosed invention and assigned by him to RohrCorporation, the assignee of the present application. This mechanismcomprises arms which are respectively fixedly attached to bars 134,links respectively pivoted to the free ends of said arms and to a ringcoaxially disposed within plug 128, and an actuator which is alsodisposed within the plug and connected to said ring and adapted to movethe same axially of said plug to thereby swing the vanes between theirinoperative and operative positionsv Since the components associatedwith the drive mechanism for the vanes are fully described andillustrated in the identified patent application, the teachings of whichare by this reference incorporated herein, they are not illustrated inthe accompanying drawings for the sake of simplification. Preferablyplug 128 is formed with elongate, shallow recesses 136 in which vanes132 are respectively received when they are retracted. Operation of theSecond Embodiment It will be understood from the foregoing descriptionthat vanes 132, when in the operative position, induce vortical motionin the exhaust gas of engine 122. Hence, the mechanism which moves saidvanes can be operated at any selected time to suppress the noisegenerated by the flow of the exhaust gas through the atmosphere. ThirdEmbodiment of the lnverltion In FIG. 8 reference number 220 designatesgenerally a third tubular aircraft housing enclosing a jet engine 222which again may be either the turbojet or the turbofan type (a turbojetengine being illustrated). Coaxially mounted on the aft end 224 ofhousing 220 is a longitudinally corrugated thrust nozzle which isdesignated generally by reference number 226. More explicitly, the wallof the nozzle is formed with longitudinally extending corrugations, orindentations, which gradually increase in depth in the downstreamdirection, the nozzle being cylindrical at its forward end to match theaft end of housing 220 and having a daisy-petal configuration at its aftend, as illustrated in FIGS. 9 and 10. The innermost portions of the aftedge of the nozzle are fixedly secured to a tear-shaped nozzle plug 228,the latter being coaxial with the nozzle and housing 220. Each lobe 230of the nozzle comprises a pair of sidewalls which extend radially fromthe innermost curved portions of the nozzle wall, and a pair ofrectangular vanes 232, 234 are respectively pivotally mounted at the aftedges of these radially projecting sidewalls of each lobe. Moreparticularly, each vane is mounted on a rod 236 (see FIGS. 11 and 12)which in turn is journaled in an aperture in the forward portion of thewall of plug 228, and the rods are spaced apart circumferentially ofsaid plug and arranged so that their longitudinal axes are respectivelyin parallel, adjacent relation with the radially projecting portions ofthe aft edges of lobes 230. Fixedly mounted within the plug is anactuator 238 which can be operated to move the drive shaft 240 thereofin opposite directions axially of said plug. A plurality of struts 242are fixedly connected at one end to the free end of drive shaft 240 andat the other end to a ring 244 which coaxially disposed with the plug.Each rod 236 projects into the interior of the plug and has a piniongear 246 on its inner end, and a plurality of gear racks 248 are fixedlymounted on ring 244 and project rearwardly therefrom the respectivelyengage gears 246. Operation of the Third Embodiment During cruise flightof the aircraft equipped with the abovedescribed propulsion apparatusvanes 232 and 234 are in the inoperative position illustrated in FIGS. 8and 9, wherein they extend downstream from the aft edges of the lobes230 of nozzle 226 and their sides are coplanar with the surfaces of theradially extending sidewalls of said lobes. When in this position thevanes obviously have no effect on the flow of exhaust gas from thenozzle lobes or the flow of slipstream air therebetween. Prior to orduring takeoff of the aircraft actuator 238 is operated to move ring 244toward the forward end of plug 228, whereupon gear racks 248 turn piniongears 246 so that vanes 232 and 234 are rotated to the operativeposition illustrated in H6. 10. Exhaust gas flowing through lobes 230 isthen deflected laterally thereof, and slipstream air flowing through thevalleys between said lobes is also deflected in the same direction,thereby imparting vortical motion to the combined streams of exhaust gasand slipstream air and thereby increasing the rate of mixing of saidexhaust gas with atmospheric air. Vanes 232 and 234 may of course alsobe placed in the operative position as the aircraft is landing, so as topermit operation of the associated jet engine 222 at high rotationalspeed while reducing thrust until thrust reversers are deployed, asdescribed hereinbefore.

Other embodiments of the invention and modifications of the disclosedembodiments will be obvious in view of the disclosure made herein. Thescope of the invention should there fore be considered to be limitedonly by the terms of the appended claims.

What is claimed as new and useful and desired to the secured by US.Letters Patent is: V

1. In an aircraft having a jet engine, the combination comprising:

a thrust nozzle through which exhaust gas of said engine is discharged;plurality of rotatable vanes for whirling said exhaust gas about thelongitudinal axis thereof at any selected time, whereby the divergenceof the jetstream discharged from said nozzle can be varied, said vanesbeing disposed adunct to said thrust nozzle and positioned upstream ofthe discharge portion thereof, said vanes having a greater surface arearadially transverse to the direction of exhaust flow than longitudinalof said flow, said transverse surface area of said vanes beingsubstantially equal to the radius of said exhaust nozzle, and said vanesbeing rotatable between (1) an inoperative position wherein they permitnormal flow of said exhaust gas substantially parallel with thelongitudinal axis of said nozzle and (2) an operative position whereinthey are spaced apart around said axis in oblique angular relationthereto and disposed within said exhaust gas to deflect impingingportions thereof circumferentially of said nozzle; and

means connected to said vanes for moving them between said inoperativeand operative positions thereof.

2. The combination defined in claim 1 wherein said vanes are featheredin said exhaust gas when in said inoperative positron.

3. The combination defined in claim 1 wherein said vanes are mounted onsaid nozzle for rotation about axes disposed radial to the longitudinalaxis thereof.

1. In an aircraft having a jet engine, the combination comprising: athrust nozzle through which exhaust gas of said engine is discharged; aplurality of rotatable vanes for whirling said exhaust gas about thelongitudinal axis thereof at any selected time, whereby the divergenceof the jetstream discharged from said nozzle can be varied, said vanesbeing disposed adjunct to said thrust nozzle and positioned upstream ofthe discharge portion thereof, said vanes having a greater surface arearadially transverse to the direction of exhaust flow than longitudinalof said flow, said transverse surface area of said vanes beingsubstantially equal to the radius of said exhaust nozzle, and said vanesbeing rotatable between (1) an inoperative position wherein they permitnormal flow of said exhaust gas substantially parallel with thelongitudinal axis of said nozzle and (2) an operative position whereinthey are spaced apart around said axis in oblique angular relationthereto and disposed within said exhaust gas to deflect impingingportions thereof circumferentially of said nozzle; and means connectedto said vanes for moving them between said inoperative and operativepositions thereof.
 2. The combination defined in claim 1 wherein saidvanes are feathered in said exhaust gas when in said inoperativeposition.
 3. The combination defined in claim 1 wherein said vanes aremounted on said nozzle for rotation about axes disposed radial to thelongitudinal axis thereof.